Well, two things come to mind.
1) Yes, All-News is a tune-out for the young. That was true all through the history of All-News radio. WINS and WCBS never had appeal to the younger demos, even in the early 70s, when they were often #4 and #5 in Arbitron. So everyone who listens to WINS and WCBS now were not likely listening 20, 30 or 40 years ago. They grew into their All-News habit.
2) What sense would it make for Audacy to watch WCBS sink into oblivion? If you have the tenth best billing station, you don't throw up your hands and say, "I give up. Bring on the foreign language brokered programming." You say, "This is a franchise we're going to keep." The billing you lose you may never get back. Whatever listeners you have tuning in to WCBS, helping you bill almost $30 million a year, you don't let them go without a fight. I think the fight includes putting the station on 94.7 FM.